1. Field of the Invention
The present invention relates generally to riveting machines, and more particularly to a portable riveting system with an autofeed mechanism for automatically supplying rivets to an application tool and methods for operating the riveting system.
2. Background and Summary of the Invention
A blind rivet comprises a tubular rivet body in which is mounted a mandrel having a head portion at the narrow end of the stem so that when the mandrel is pulled back in the rivet, it upsets the rivet. When pulling-back of the mandrel is resisted with a predetermined force, the mandrel breaks off. A riveter that operates with such rivets typically has a housing formed at its front end with an aperture through which the rivet mandrel is engaged. Within the housing is a chuck that engages tightly around the mandrel and an actuating mechanism or pulling head which pulls the chuck backwardly, thereby upsetting the rivet and breaking off the mandrel.
In rivet setting machines, the operator sets a rivet held in the nose of the rivet tool by pulling a trigger. The remaining spent mandrel is drawn through the tool and through a collection tube into a collection box. A proximity switch senses the spent mandrel just before it enters the collection box.
There are a variety of different types of tools, both manual and powered, that are used to set pull-type blind fasteners. For industrial production, it is desirable to use a power tool that may have an air/hydraulic or electrical power assist to pull the mandrel stem. This facilitates the rivet setting operation.
It is known to automate the process of feeding rivets to the riveter tool, as for example shown in U.S. Pat. Nos. 4,754,643 and 4,747,294, commonly assigned. It is also known to automate the mandrel collection process as taught, for example, in U.S. Pat. No. 4,972,985, also commonly assigned. The most common approach to automatic rivet feed and disposal uses hydraulically or pneumatically powered mechanisms for guiding blind rivets to the riveting tool and extracting broken off mandrels therefrom.
Common shortcomings of prior art apparatus for autofeeding of rivets to the riveting tool is the failure of such systems to take into account the need for rapid adjustment, improved maintenance, serviceability and rapid change-over capability. In addition, ways are constantly being sought which speed up the reload capabilities as well as speeding up the rivet setting process.
In furthering the above and additional objects, the present invention provides a rivet setting tool including an automatic rivet delivery device for transferring a rivet from a rivet passage to a nose piece of the rivet setting tool. The rivet delivery device is air driven to extend forwardly of the nose of the setting jaws, and rotates to present a rivet in front of the jaws and then transfers the rivet into the jaws in known manner. The rivet delivery device extends through the rear of a hand tool so that its angular rotation can be adjusted without disassembling the tool. The stroke length of the rivet delivery device can also be easily adjusted.
A further feature of the rivet delivery device is the provision of a double-acting piston driven in both directions by positive air pressure to extend and rotate the delivery device in front of the nose piece and returning the rivet delivery device after rivet transfer. The use of a double-acting piston greatly enhances the speed at which the rivet delivery device can operate. Furthermore, the ability to adjust the stroke length or angular rotation of the rivet delivery device without disassembling the entire tool, greatly increases the ability to rapidly adjust the rivet delivery device in order to change over to different sized rivets or to simply make minor adjustments.
The system of the present invention also includes a portable housing and a hand tool connected to the portable housing. The portable housing includes electronic and pneumatic modules for controlling the supply of electric and pneumatic power to a rivet feeding device and to the hand tool. In response to the activation and release of a trigger switch on the hand tool, blind rivets are supplied from a feeder bowl via a track to a reciprocating escapement mechanism which transfers successive rivets from the track to a tube through which they are moved by compressed air to a rivet delivery device located on the hand tool. The different components of the portable autofeed riveting system are designed to be separately detachable from the housing as a modular unit so that the independent modular units can be easily disassembled from the housing and can be replaced by replacement modules so that the rivet setting tool experiences as little down time as necessary.
The portable rivet setting system of the present invention is also provided with an escapement mechanism which includes a nesting block slidably received by a housing and including a recessed portion for receiving and supporting a fastener therein. The nesting block can be easily changed in just a few seconds in order to accommodate a different sized rivet. The ability to rapidly change the nesting block reduces the amount of time required for change over, and thereby increases the efficiency of the overall riveting system.
The rivet setting tool of the present invention is provided with a pulling head which employs air pressure to return the piston to its full forward position and is connected to a remote intensifier via a hydraulic hose. The remote intensifier includes an air piston disposed in a piston chamber and a hydraulic ram connected to the air piston and extending into a hydraulic passage connected to the hydraulic hose. The air piston has a larger cross-sectional area than the hydraulic ram which allows the intensifier to generate a large hydraulic pressure from a relatively small air pressure. A first supply of pressurized gas communicates with a first end of the piston chamber and a second supply of pressurized gas communicates with a second end of the piston chamber. The second end of the piston chamber is vented to atmosphere around a piston chamber sleeve. The second supply of pressurized gas is utilized to provide a low pressure bubble of air on top of the air piston in order to assist the return of the piston of the pulling head to a retracted position while increasing the speed of the piston's return. The speed at which the air piston returns to its retracted position is directly related to the speed at which the rivet setting tool is reset in order to receive and set another rivet.
The rivet setting tool of the present invention is also provided with a control strategy whereby when a trigger is depressed, a controller instructs the remote pulling head back in order to set a rivet. The jaws engage the rivet mandrel and start the setting process. As hydraulic pressure builds, a high and a low pressure switch witness the increase in pressure as setting occurs, and set a latch. When the high pressure switch drops low again, the controller deduces that the rivet has set. Activation pressure to the remote intensifier is then stopped and return air is started causing the tools pulling head to return concurrently. The controller starts a mandrel collection window to monitor the collection of the mandrel. As the tool jaws open, the mandrel is released and a vacuum draws the mandrel past a mandrel sensor and into the collection bin. As the mandrel passes the mandrel sensor, the mandrel collection window is reset. The rivet delivery device loads a new rivet into the nose piece of a tool as the tool returns full forward. Since the high setting/loading speed makes it possible to have as many as two mandrels in the collection path at once, two separate mandrel collection windows are required, with the first becoming available for the third rivet as soon as the first mandrel passes the mandrel sensor. These two timers (windows) are continuously reused again and again throughout the process. If a jam were to inhibit collection of the mandrels as witnessed by the window timing out before the mandrel sensor detects a mandrel's passage, the system will shut down.
The pressure switches allow the system of the present invention to determine if there is a rivet loaded in the nose of the tool since no sensor is provided in the nose of the tool. During the setting process, the system confirms that a rivet has been loaded by monitoring the pressure switches. If the switches detect pressure within a short period of time, i.e., within an amount of time for the pulling head to travel almost fully back, it knows a rivet was presented and proceeds as above. If there were no rivet in the nose of the rivet setting tool, when the trigger is activated, the switches would see no build-up of pressure within the setting window and would not start a mandrel collection window, but would rather initiate the rivet delivery device reloading sequence.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.